We assume that the response to extended maternal separation reflects the developing organism's capacity for a complex affective response, and represents the core upon which more pathological depressive responses build. The developmental course of this psychobiological response complex remains unstudied in children under 6 years. We propose to examine it by: 1) testing and validating new methods for assessing depression-like responses in this age group so that continuities with older children can be traced and early diagnostic criteria established; 2) describing the age related shifts in the clinical picture to understand better the underlying phsychopathological processes. An experimental group of children separated from their mothers for six days due to maternal hospitalization, and a control group will be studied at three age periods: 9-18 mos.; 21/2-41/2 yrs, and 6-8 yrs. Measures of separation response will adhere closely to the criteria accepted for a diagnosis of depression in older subjects. We have devised special instruments for assessing these criteria in our population. These include: 1) a Kiddie-Infant "Depression Observation Scale (KIDOS) which scores a profile of prevailing affect states, social interest, anhedonia, attention, aggressiveness, negativism and regression, using a behaviorally defined score of T.V. recorded behaviors; 2) evaluation of sleep activity, kusing time-lapse T.V. recording; 3) motor activity, using an actometer; 4) appetite, using a questionaire. Constellations of the separation response as a function of chronological age will be derived from analyses. Because verbal report of subjective state is so important, but unavailable at these young ages, we have devised experiments to circumvent this limitation based on the principle that affect state influences perception. We will assess how subjects attend to, perceive and/or remember faces, colors or story elements graded along the hedonic dimension of happy-sad A smaller group of 6-8 yr. old clinically depressed children will be evaluated and compared on our procedures and standard instruments with age-matched control and separated subjects to help establish the validity of our assessment methods and the relatedness of extended separation responses to the clinical picture of frank depression.